Gas control means for grenade launching attachments



April 7, 1964 c. A. MOORE 3,127,591

GAS CONTROL MEANS FOR GRENADE LAUNCHING ATTACHMENTS Filed June 27, 1962 2 Sheets-Sheet 1 Q 9 00 m I l INVENTOR. H Qyril A MDUTE BY I j Mnma; w

April 7, 1964 c. A. MOORE 3,127,691

GAS CONTROL MEANS FOR GRENADE LAUNCHING ATTACHMENTS Filed June 27, 1962 2 Sheets-Sheet 2 IN VENTOR.

p yril A MEID1E BY United States Patent Office 3,127,691 GAS CONTRQL MEANS FOR GRENADE LAUNCI-HNG ATTACHMENTS Cyril A. Moore, Springfield, Mass., assignor to the United States of America as represented by the Secretary of the Army Filed June 27, 1962, Ser. No. 205,805 6 Claims. (Cl. 42-1) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to the launching of relatively large and heavy projectiles from the muzzle end of a firearm barrel and is particularly directed to an attachment which can be utilized to launch comparatively thinwalled grenades without the necessity for a corresponding reduction in the quantity of discharge gases directed thereagainst.

Current military rifles are customarily provided with special attachments which enable the user to discharge projectiles, such as grenades, in lieu of the conventional ammunition for which the weapon is designed. These attachments hold the grenade projectiles in the path of the gases generated by the discharge of a relatively powerful blank cartridge in the firing chamber of the barrel. As a result, the advantages of grenade ammunition can be obtained at considerably greater ranges than heretofore possible.

Although the above procedure provides highly satisfactory results with standard grenade ammunition, considerable difficulty has been experienced in the firing of grenade projectiles of advanced design in which the thickness of the walls has been substantially reduced. It has been found that the rapid expansion of the discharge gases in a confined area, such as a firearm barrel, produces a jet stream of sufficient intensity to pierce the relatively thin wall forming the base of the grenade projectile. Inasmuch as the necessity for a minimum crosssection in the grenade walls is an essential military characteristic which cannot be eliminated, the prevention of damage to the base of the projectile must be accomplished in some manner other than the obvious expedient of increasing the wall thickness thereof. Furthermore, it has been demonstrated that, even in those instances in which the grenade projectiles are not actually damaged, the jet effect of the rapidly expanding discharge gases is not necessarily located along the central axis thereof and, consequently, produces a significantly greater pressure on one-half of the arcuately formed base of the projectile than on the other. As a result, the grenade is launched with a degree of spin capable of producing actual curvature in the flight path thereof. In view of the importance of securing maximum range in the flight of the grenade projectile, the obvious solution of reducing the powder charge in the blank cartridge cannot be considered.

Accordingly, it is an object of this invention to provide a device for launching relatively large and heavy projectiles from the muzzle end of a rifle barrel at a greater range than heretofore possible.

An important object of this invention is to provide a grenade launching device of the aforesaid type which will increase the uniformity of the gas pressure directed at the base of the grenade projectile without any appreciable reduction in the degree of thrust thereagainst.

It is a specific object of the present invention to provide a grenade launching device in which control means are specifically provided to prevent the discharge gases from forming a jet stream in the area between the muzzle 3,1216% Patented Apr. 7, 1964 end of the rifle barrel to which the device is attached and the base of the grenade projectile to be launched therefrom.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is an elevational view in partial section show ing the grenade launching device of the present invention attached to the muzzle end of a rifle barrel;

FIG. 2 is a transverse section taken along line 22 in FIG. 1 to show the configuration of the control member as seen from the rear end thereof and also shows the grenade launching device in the open position in which the grenade projectile is loaded into the firing tube;

FIG. 3 is a perspective view of the control member;

FIG. 4 is an enlarged elevational view of a modified control member;

FIG. 5 is a rear end View of the control member of FIG. 4; and

FIG. 6 is a longitudinal section taken along line 66 of FIG. 4 showing the tapered configuration of the body portion of the control member.

As shown in FIG. 1, military firearms, such as the 7.62 mm. Springfield M14 rifle, can be utilized for the launching of grenade ammunition through the addition of an attachment adapted to hold a launching tube 10 in axial alignment with the muzzle end of a rifle barrel 12. Such attachment includes an adapter 14 having a yoke 16 in the forward end thereof arranged to threadably receive the rear end of launching tube 10'. Adapter 14 is formed with a rearwardly projecting hollow cylindrical extension 18 which is releasably secured to the forward end of a mounting bracket 20. The rear end of bracket 20 is provided with a pivotal latch 24 adapted to engage a suitable lug 26 depending from a gas cylinder 28 secured to the underside of barrel 12 as is customary in gas operated firearms of the military type. The lower end of yoke 16 is pivoted at 30 in adapter 14 for movement between the firing position shown in FIG. 1 and the loading position illustrated in FIG. 2. A spring-biased plunger 32 in the upper end of adapter 14 is utilized to lock yoke 16 in the firing position. When plunger 3-2 is pushed forwardly out of engagement with yoke 16, a torsion spring 34 automatically pivots yoke 16 and launching tube 10 carried thereby to expose the rear end of the latter for the reloading of a grenade round therein.

While the foregoing attachment has been satisfactorily utilized in the launching of conventional rifle grenades, considerable difiiculty has been encountered in the launching of grenades in which the wall thickness thereof has been substantially reduced. This type of grenade ammunition is illustrated in FIG. 1 and essentially comprises a fragmentation type projectile having a cylindrical body 36 terminating in semicircular ends 38. The reduced wall thickness, indicated at 40, is substantially uniform throughout both body 36 and ends 38. In order to stabilize the flight of the grenade projectile, the bore of launching tube 10 is rifled, as shown at 42, and, consequently, projectile body 36 is provided with an annular band 44 about the exterior adapted to be engraved by rifling 42.

Extensive firing of the relatively powerful blank cartridges required for the launching of grenades from rifles has revealed that the discharge gases are concentrated into a jet stream prior to impact against the base of the grenade projectile. The extremely high'velocity of such jet stream results in serious erosion of the relatively thin walls of the grenade projectile and in many instances produces actual penetration thereof. Further- =3 more, even if the damage to the walls of the grenade projectile can be disregarded, the powerful thrust of the culties may be virtually eliminated by the insertion of a control plug 46 between the muzzle end of rifle barrel 12 and the rear end of launching tube 10. Plug-46 is-a cylindrical member having an exterior diameter equivalent to that of rifle barrel 12 and is positioned in axial alignment therewith by a tubular housing 48 threaded into the interior of adapter extension 18. The rear end of housing 48 is enlarged, as shown at 50, andis threadably mounted in bracket to engage the muzzle end of rifle barrel 12. The forward end of housing 48 is inwardly turned to block forward movement of gas control plug 46.

As best shown in FIG. 4, the exterior periphery of plug 46 is helically grooved along the entire length thereof, as indicated at 54, to form a plurality of radially disposed helical ridges 56. When plug 46 is inserted into housing 48 preferably With a drive fit, ridges 56 cooperate with the interior bore of housing 48 'to'form'a plurality of passages for the discharge gases emerging from barrel 12. While the depth of grooves 54 and the length of gas control plug 46 will vary in accordance with the degree of helical dispersion desired in the discharge gases, the helical pitch of grooves 54 must be suflicient to permit the forward end of each ridge 56 to extend slightly beyond the rear end of the adjacent preceding ridge as viewed in a clockwise direction. Thus, it will be impossible for the discharge gases to pass through control plug 46 without being diverted into a helical path by the sides of ridges 46. Obviously, this diversion in the path of the discharge gases will nullify any jet streameflect which may be produced upon emergence from rifle barrel 12.

While helical grooves 54 and ridges 46 are'preferably symmetrically formed throughout the entire length of gas control plug 46 and, therefore, provide a reversible member for ease in assembly, it is also within the concept of the present invention to increase the helical twist at a faster rate at one end than at the other. Furthermore, is also may be desirable in some instances to provide a greater gas passage area in the rear end of control plug 46 than in the forward end thereof. This may be readily accomplished by a uniform decrease in the depth of grooves 54 which will provide a tapered body 58 as best .shown in FIG. 6.

If desired, maximum efliciency of control plug 46 may be achieved by reducing the planar area in the path of the discharge gases. As best shown in FIG. 5, this may be accomplished by an arcuate bevel 57 at the origin of each helical groove 54 beginning at adepth which is slightly offset from the axial center of the body portion of plug 46 and extending forwardly therelalong to blend into tapered body 58. Thus, eachgas passage is provided with an entry portion 59 of maximum area which produces a corresopnding minimum area of planar configuration in the path of the discharge gases. At the same time, the lateral extent of each bevel 57 is progressively enlarged in a radial outward direction to form a relatively sharp point 60 at the onigin of each ridge 56. The foregoing configuration of control plug 46 will, of course, facilitate the entry of the discharge gases into a helical path of movement without any substantial reduction in the ultimate pressure thereof against the rear end of the grenade.

Thus, there is here provided a simple yet positive means of eliminating the undesirable results of the jet stream effect ordinarily encountered in the discharge gases produced by the firing of a blank cartridge in order to launch a grenade projectile from a rifle.

The inclusion of the gas control plug of this invention in a grenade launching attachment for military rifles permits safe firing of hollow grenade projectiles even though the wall thickness thereof is far less than that utilized in conventional grenade ammunition of this type. Furthermore, the ability of the gas control plug to diffuse the flow of the discharge gases provides the additional benefit of increased accuracy and range in the flight path of the grenade.

Although a particular embodiment of the invention has been desribed in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the followingclaims are intended to include such variations.

I claim:

1. In a firearm barrel attachment for launching a relatively thin-walled grenade inresponse to the discharge of a powerful blank cartridge in the barrel, the combination of a rifled tube for holding the grenade in position to be launched, means for releasably mounting said tube in axial alignment with the muzzle end of the barrel, and a gas control plug disposed in the direct path of the discharge gases evolved upon the firing of the blank cartridge, saidplug having aplurality of helical gas passages along the exterior thereof of sufficient length and pitch to rotate the entire quantity of discharge gases into substantially uniform contact with the grenade.

2. In a grenade launching attachment releasably secured to the muzzle end of a firearm barrel, a rifled launching tube spaced forwardly of the barrel in axial alignment therewith, a gas control plug fixedly mounted in the path of the discharge gases evolved in the barrel, saidplug having a plurality of helical ridges spaced about .the exterior periphery thereof to define gas passages therethrough, the length and pitch of said ridges being suffi- .cient to position the forward end of eachridge at least .in axial alignmentwith the rear end of the next adjacent ridge as viewed in a clockwise direction.

3. The combination defined in claim 2 wherein the depth of said gas passages is a maximum at one end and progressively decreases to the opposite end thereof.

4. The combination defined in claim 2 wherein the .entry end of each of said gas passages is formed with an arcuate bevel originating in offset relation to the axial center of said plug to provide-minimum interference with the entry of the discharge gases therein.

5. The combination defined in claim 4 wherein the lateral extent of said arcuate bevel is progressivelyincreased in a radial direction to form relatively sharp .points at the beginning of said ridges.

6. In an attachment releasably secured to the muzzle .end of a firearm barrel for launching a grenadetherefrom, .a rifled launching tube having a bore of greater diameter than the bore of the barrel and in axial alignment therewith, and a gas control plug of substantially the same exterior diameter as that of the barrel and fixedly mounted in the path of the discharge gases emanating therefrom, said plug having a plurality of helical gas passages-there- ,through openinginto said launching tube bore for rotating the gases to exert substantially equal pressure against .the entire rear end of the grenade.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A FIREARM BARREL ATTACHMENT FOR LAUNCHING A RELATIVELY THIN-WALLED GRENADE IN RESPONSE TO THE DISCHARGE OF A POWERFUL BLANK CARTRIDGE IN THE BARREL, THE COMBINATION OF A RIFFED TUBE FOR HOLDING THE GRENADE IN POSITION TO BE LAUNCHED, MEANS FOR RELEASABLY MOUNTING SAID TUBE IN AXIAL ALIGNMENT WITH THE MUZZLE END OF THE BARREL, AND A GAS CONTROL PLUG DISPOSED IN THE DIRECT PATH OF THE DISCHARGE GASES EVOLVED UPON THE FIRING OF THE BLANK CARTRIDGE, SAID PLUG HAVING A PLURALITY OF HELICAL GAS PASSAGES ALONG THE EXTERIOR THEREOF OF SUFFICIENT LENGTH AND PITCH TO ROTATE THE ENTIRE QUANTITY OF DISCHARGE GASES INTO SUBSTANTIALLY UNIFORM CONTACT WITH THE GRENADE. 